The optical module to transmit and/or receive optical signals, generally includes a package that installs semiconductor optical devices, such as a semiconductor laser diode (hereafter denoted as LD) or a semiconductor photodiode (hereafter denoted as PD), and an optical receptacle to couple the semiconductor optical device with an external fiber.
One type of the optical module has an arrangement that the semiconductor optical device is mounted on a lead frame, and both of them are encapsulated with a transparent resin. A Japanese Patent Application published as JP-2004-133117A has disclosed such an optical module that encapsulates a lens, in addition to the optical device and the lead frame, within the sealant to compensate the degradation of the optical coupling between the optical device and the external fiber due to larger temperature dependence of the refractive index of the transparent resin to encapsulate the members. However, the lens encapsulated in the sealant is easily misaligned by the fluid resin during the molding, which increases the optical coupling loss between the device and the external fiber.